Paint going to dust

A couple of the models that I built a few months back, are experiencing their paint jobs turning into a powder.
The surfaces are enamel, either from Tamiya's or Humbrol's paint range, but
more so the Humbrols.
Black is currently the worst of the colours at the moment, as it basically has been removed with just a feather duster.
Any ideas?
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W wrote:

What are the conditions in your home? I've never encountered that with model paint.
Bill Banaszak, MFE
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I started noticing it around Christmas, that is just before we started having the 35C+ days.
The area that I currently have the models is rather cool even when it was 38C outside, and has very good ventilation - the air is never stale even when the doors and windows are closed.
The only things I can come up with to explain the dusty nature of the paint: 1) Far too thin, but then it isn't because in one coat I can cover any light/bright colour. 2) Paint was contaminated with some caking agent - this has been the only time I have ever seen something that even closely resembles what I am experiencing.
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Hi W,
I always varnish mine with Xtracolour matt/semi-matt after painting them and have had no problems.
So that could be a solution, unless you are varnishing them and you are gettting a bad reaction with the type you are using with Tamiya/Humbrol paints.
Cheers, Stephen
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and
I have not arrived at that stage just yet, but I do have intentions of applying a finish to seal the paint.
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Sounds to me like the paint was too thick or maybe the word should be dry- it covered well - a sign of not being too thin. If it was too thick it would dry on the way to the model and just lay on the surface. I once had a problem where the paint dried on the way in and the surface looked like tiny balls instead of smooth - easily rubbed off for a correct coat. Too thin and it would lay on the surface and tend to run.
Two other possibilities - one surface preparation. Did you wash the mold release off the model, and maybe later finger print oils, or you used the wrong thinner and it did something strange of a chemical nature to screw up the paint coat;.
This seems like a topic that needs more discussion - Hate to have it happen to me - would be nice to know the reason - especially if its the basic paint thats at fault.
Val Kraut

but
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I'm no expert, but it sounds to me as if the paint was missing one of its constituent parts - some sort of binder, maybe.
RobG

basically
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Rob Grinberg wrote:

Can we assume it was well stirred? I've gotten uneven results on occasion because Humbrol's wasn't as well stirred as I thought I had it. I've never used Tamiya's paints so I'm no help there.
Bill Banaszak, MFE
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its
I use a battery operated agitator which works very well for the Humbrol mud.
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W wrote:

Then that doesn't sound like the cause. I'm out of ideas now.
Bill Banaszak, MFE
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i whupped up a bahgun shaker. took the guide plate off my 'lectric jig saw. i tape the paint or jar to the blade, lay it on the carpet and block the trigger on with another bottle. ten minutes and the clumpiest is smooth.
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Good idea - I've seen the same done with orbital sanders. Just make damn sure that lid is on *tight*!
RobG

of
it.
mud.
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tighter than a weldiggers....
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I just got back from the workshop, I ran a white rag over the surface...nothing. Not a smudge, smear, speck, spock of paint dust.
I am starting to sway my thinking in a different direction: soot.
I use a candle to nullify the vapours (yes I know, but it is on the other side of the room, and at no point does it get that concentrated), and am starting to wonder if there may be soot coming from it.
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basically
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I think you will find Tamiya paints are Acrylic which means there isn't a problem with the type of paint. It probably is the paint drying into tiny globules on it's way to the model and not being able to spread out once it hits the surface, try rubbing over the surface with an old hankie and see if the "dust" comes off and leaves the base colour still there. if that works then next time hold the airbrush a little nearer the model or try not to use too much thinners. good luck
--
Ted (happy modeller) Taylor
http://www.modelwork.freeserve.co.uk
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In this case it is their enamal paint.

model
over
airbrush
The paint is touch dry in 5mins, I thought I had over thinned the pint, but when it comes out of the bottle it covers even white very well.
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